Pump Control

ABSTRACT

A method for configuring a drive to control the operation of a pump in a sewage system is disclosed. The method comprises measuring at least one parameter of the sewage system; using the measurement of the at least on parameter to create an algorithm for the drive to control the operation of the pump; and configuring the drive to use the algorithm to control the operation of the pump.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit and priority of Great Britain PatentApplication No. 1305054.7 filed Mar. 19, 2013. The entire disclosure ofthe above application is incorporated herein by reference.

FIELD

This disclosure relates to pump control, in particular to the control ofa sewage pump by a drive.

BACKGROUND

In a sewage system, sewage from, for example, a household, is to betransported through a pipeline to a water treatment system. Thetransport occurs mainly due to gravity, but there is often at least onepart of the sewage system that requires the sewage to be raised up. Thisis commonly achieved by a sewage pump at a sewage pumping station.Sewage arrives at the sewage pumping station and collects in a wet well.A sewage pump acts to pump the sewage upwards, often by the use of animpeller in the sewage pump.

The pump is powered and controlled by a drive (also known as a driveunit), which may be situated away from the pump outside the wet well,and may power the pump using a cable between the drive and the pump.Such a drive is able to control the frequency of rotation of theimpeller in the pump.

Given the nature of the material being pumped, it is possible for theimpeller in the pump to become clogged up and/or for material to becomestuck to the impeller, thereby decreasing the effectiveness of the pump.This is known as “ragging”. In order to restore the pump to its fulloperability, it is necessary for the pump to be cleaned (known as“de-ragging”). Manual cleaning of the pump is expensive and involves thepump having to be taken out of action while it is cleaned. A preferredde-ragging method is for the drive to carry out a cleaning mode, inwhich the frequency of rotation of the impeller is varied such that thematerial on the impeller is removed from the impeller. The routinecarried out by the pump in the cleaning mode typically takes a fewminutes.

It has been established by the inventors that, in current systems, thecleaning mode is sometimes initiated based on a “false alarm”. Forexample, the drive may monitor certain conditions in order to establishwhether ragging has occurred, and will initiate the cleaning mode whenthese conditions are found. However, different pumps in differentpumping stations experience different conditions due to their situationwithin the sewage system, such that the monitored conditions for onepump may indicate that ragging has occurred, whereas in fact it has not.Analogously, it is also possible that a drive would not detect raggingsuitably early for a pump in other operating conditions.

Such situations reduce the efficiency of the pump, either by initiatingthe cleaning mode unnecessarily, or by allowing ragging to occur for aprolonged period before it is fixed.

SUMMARY

An invention is set out in each of the independent claims. Optionalfeatures are set out in the dependent claims.

According to an aspect there is provided a method for configuring adrive to control the operation of a pump in a sewage system, the methodcomprising: measuring at least one parameter of the sewage system; usingthe measurement of the at least one parameter to create an algorithm forthe drive to control the operation of the pump; and configuring thedrive to use the algorithm to control the operation of the pump.According to an aspect there is provided a drive configured by thismethod.

According to an aspect there is provided a method for creating analgorithm for a drive to operate a pump in a sewage system, the methodcomprising: measuring at least one parameter of the sewage system; andusing the measurement of the at least one parameter to create analgorithm for the drive to control the operation of the pump. Accordingto an aspect there is provided a computer-readable medium comprising analgorithm created by this method.

According to an aspect there is provided a drive configured to controlthe operation of a pump in a sewage system using an algorithm created bya method comprising: measuring at least one parameter of the sewagesystem; and using the measurement of the at least one parameter tocreate the algorithm.

According to an aspect there is provided a sewage pumping stationcomprising at least two pumps controlled by respective drives accordingto one of the drives described above, wherein the algorithm created foreach respective drive is different.

In some embodiments, the drive is configured to use the algorithm todetermine when to implement a cleaning mode of operation for the pump.

In some embodiments, the algorithm is configured to calculate anexpected electric current for the drive for a given operating conditionof the drive.

In some embodiments, the expected electric current is the active currentdrawn by the pump.

In some embodiments, the drive is configured to monitor an actualelectric current in use corresponding to the expected electric current.

In some embodiments, the drive is configured to compare the actualelectric current with the expected electric current for the presentoperating condition of the drive.

In some embodiments, based on the comparison of the actual electriccurrent with the expected electric current, the drive is configured todetermine whether to alter the operation of the pump.

In some embodiments, the at least one parameter comprises an outputfrequency of an alternating current output by the drive.

In some embodiments, the at least one parameter comprises a wet welllevel of a wet well in the sewage system, the wet well being associatedwith the pump controlled by the drive.

In some embodiments, the at least one parameter comprises a number ofpumps active in a sewage pumping station in the sewage system, thesewage pumping station comprising a plurality of pumps including thepump controlled by the drive.

In some embodiments, the at least one parameter comprises an outputfrequency of an alternating current output by another drive in a sewagepumping station in the sewage system, the sewage pumping stationcomprising a plurality of pumps including the pump controlled by thedrive.

In some embodiments, the drive is one of a plurality of drivesconfigured to operate in the sewage system, each of the drives beingconfigured to drive a respective pump of a plurality of pumps in thesewage system.

In some embodiments, the sewage system comprises a sewage pumpingstation, in which the pump is situated.

In some embodiments, the sewage pumping station comprises a plurality ofpumps, each of the plurality of pumps being operable by a respectivedrive.

In some embodiments, the drive is configured to communicate with atleast one other drive associated with a respective other pump in thesewage pumping station.

In some embodiments, the drive is configured to communicate with atleast one other drive associated with a respective pump in anothersewage pumping station in the sewage system.

At least some of the aspects and embodiments described herein provide anumber of advantages, some of which are now described.

As the pump operates more reliably, there is less likely to be a needfor manual cleaning or maintenance of the pump. This reduces the amountof time the pump would be out of action for such maintenance. The amountof time the pump is out of action is also reduced by minimising thenumber of “false alarm” cleaning mode initiations. Energy is saved dueto the reduced power requirements of a clean pump as opposed to a pumpthat has undergone ragging.

The measurements made, which are used in creating the algorithm, ensurethat the drive is configured appropriately for the particular operatingenvironment of the pump that it is to control. The drive will thereforeoperate more effectively than if it were merely using a generalalgorithm not specific to its own operating environment. This isparticularly the case when the sewage system comprises a plurality ofpumps, with each pump being controlled by a respective drive. Some ofthe plurality of pumps may be situated in the same pumping station asthe pump controlled by the drive, and/or some of the plurality of pumpsmay be located in other pumping stations in the sewage system, which maybe upstream or downstream of the pumping station containing the pumpcontrolled by the drives.

When there is more than one pump in the same sewage system, the pressureexperienced by one pump in the system will vary due to the effects ofthe other pumps. This therefore alters the conditions of the drive inwhich the cleaning mode should be initiated. Due to the measurementsmade, the situation of the pump within the sewage system can beaccounted for.

In some embodiments, each drive in the sewage system is provided withits own algorithm that is tailored to its specific operatingenvironment.

In some embodiments, the drive communicates with other drives in itspumping station and/or in other pumping stations to ensure that one ormore of the other pumps controlled by the other drives is not already ina cleaning mode if it is determined that the drive should initiate thecleaning mode for its pump. In such a situation, the drive would waitfor the other pump to finish its cleaning mode before initiating its owncleaning mode.

DRAWINGS

FIG. 1 depicts schematic diagrams of four sewage systems;

FIG. 2 depicts a schematic diagram of a sewage pumping station; and

FIG. 3 depicts a flow diagram illustrating the processes involved in thepresent disclosure.

DETAILED DESCRIPTION

With reference to FIG. 1, first, second, third and fourth sewage systemsare described. Each sewage system comprises at least one sewage source(for example, a household, building or town), which is connected to awater treatment system by at least one pipeline. At least one sewagepumping station is positioned along the pipeline between at least one ofthe sewage sources and the water treatment system.

The first sewage system comprises a single sewage source, a singlepipeline and a single sewage pumping station along the pipeline. Thesecond sewage system comprises two sewage sources, each having arespective pipeline and sewage pumping station in parallel, whichcombine to form a single pipeline before the water treatment system isreached. The third sewage system is similar to the first, but has aplurality of sewage pumping stations in series along the pipeline (inthis example there are three sewage pumping stations). The fourth sewagesystem is similar to the second sewage system, but this system has aplurality of sewage sources each having its own pumping station, and therespective pipelines then successively combine in turn (in this examplethere are four sewage sources and four respective sewage pumpingstations).

With reference to FIG. 2, a sewage pumping station is described in moredetail. The sewage pumping station comprises a wastewater well (alsoknown as a wet well), in which sewage is collected, having arrived froma sewage source, or an earlier sewage pumping station along thepipeline. A pump is situated inside the wastewater well, proximal to thebottom of the wastewater well, and is used to pump sewage up through thefollowing pipeline, as described above. The pump comprises an impeller(not shown). The pump is controlled by a drive. In this sewage pumpingstation, a plurality of other pumps is also contained within thewastewater well, each of these other pumps being controlled byrespective other drives. The drives are situated outside the wastewaterwell, and control the respective pumps via a respective cable. In thisembodiment, the pumps in the sewage pumping station are configured torun in a constant flow regime (in normal use).

With reference to FIG. 3, the development and use of an algorithm forthe drive is described. The algorithm is tailored specifically to thedrive, which may correspond to any of the drives in any of the sewagepumping stations in the various sewage systems shown in FIG. 1, or othersuch sewage systems.

In developing the algorithm for the particular drive, first, ameasurement phase is carried out, in which one or more parameters of thesewage system are measured. In this embodiment, the parameters measuredare an output frequency, an active current, a wastewater well level, afrequency of other pumps and a number of pumps active. The outputfrequency is the frequency of the AC current output of the drive, whichcorresponds to the frequency of rotation of the impeller of the pump,enabling the speed (flow rate) of the pump to be measured. Thisparameter is derivable from the drive. The active current is the activecurrent drawn by the pump. This parameter is derivable from the drive.The wastewater well level is the height of the fluid contained withinthe wastewater well measured from the bottom of the wastewater well,which varies over time and depends upon the rate of flow into thewastewater well and the rate of flow out of the wastewater well throughthe pumps. This is measured directly from the wastewater well, using ameasuring device. The frequency of other pumps provides the sameinformation as the output frequency, but for the other pumps in thesewage pumping station. This parameter is obtained from a communicationpath between the particular drive and the other drives. The number ofpumps active is the number of the other pumps in use in the sewagestation, which enables the drive to be configured with an awareness ofthe effects of the other drives in the sewage pumping station. Thisparameter is derivable from the frequency of other pumps, with thosehaving zero frequency being inactive.

The measurement phase may last for up to several weeks, in order toobtain a detailed set of data for the whole system taking into accountall of the variables.

The raw data from the measurement phase is recorded and analysed. Thedata is plotted into a graph for each day, which enables a trainedengineer to recognise patterns, and in particular recognise at whichpoint the pump has been manually cleaned by the end-user (this resultsin a sudden change in the measured active current after a start of thepump). The data identified as corresponding to a time immediately aftera manual cleaning of the pump is used to determine the characteristicsof the pump (known as the pump curve).

The measurements from the measurement phase are used to create analgorithm. The algorithm is configured to calculate an expected electriccurrent for the drive. The expected electrical current is the activecurrent drawn by the pump. The active current provides an accuraterepresentation of the power used by the pump (and hence the torqueproduced by the pump).

The expected electrical current is calculated by taking into accountparameters measured in real time and inputting these into the algorithm,which has been prepared in advance based on the measurements from themeasurement phase. The measured parameters used by the algorithm are thepump curve (also known as the pump characteristics), the system curve(also known as the system characteristics), the influence of the otherpumps in the system and the wastewater well level. The influence of theother pumps in the system is relevant because the pressure in the sewagesystem varies due to other pumps in the sewage system. These pressureeffects will therefore affect the measurement of torque of the impellerderived from the current measurement. The wastewater well level ismeasured by a measuring device and enables the amount of sewage in thewastewater well to be determined.

Data identified as corresponding to a time immediately after a manualcleaning of the pump is used as the start position for the algorithm.The data is filtered and categorised to represent an active current inthe different situations that occurred during the measurement phase. Thedifferent situations are the variable frequency, the wastewater welllevel and the frequency of the pumps at the sewage pumping station, andpotentially also including pumps in another station on the samepipeline.

Extreme high and low values are filtered to achieve a representativecharacteristic for each possible situation. The representativecharacteristics are again analysed, and are displayed in graphs. Thegraphs are analysed and a function or combination of functions is set upto model the graphs for each analysed situation of the system. Themathematical functions created comprise a combination of linear andsquare functions with an offset on the starting point of the function.In some less-complicated systems, a step-response with a few set pointswill suffice.

The created functions are used to produce the algorithm, which takes thevariables into account. The created algorithm is implemented in softwarerunning on an application module fitted in the drive. To test thealgorithm and ensure its accuracy, the expected electrical currentcalculated by the algorithm is recorded together with other datameasured in use. This data is then analysed and used to create a newgraph. When the algorithm is working correctly, the difference betweenthe expected electrical current and the measured active current for aclean pump will be close to zero (typical values are less than onepercent of the nominal full load current).

After testing the algorithm to ensure its accuracy, the pump ismonitored for a few days to see if the software is able to detect dirtat an early stage and successfully de-rag the pump. Some fine-tuning maybe applied to optimise the performance of the system by keeping theamount of cleaning cycles as low as possible without getting anexcessive build-up of dirt to a point where manual cleaning is needed.

The output of the algorithm is the expected electrical current. This isthen used in a determination phase, in which it is determined whetherthe drive is to implement a cleaning mode for the pump, as is nowdescribed.

When the drive is in use, the expected electric current output from thealgorithm is compared with the actual electric current derived from thedrive. The actual electric current is a measurement of the same type ofcurrent as that output by the algorithm, i.e. in this embodiment theactive current. At block A, the difference between the expected electriccurrent and the actual electric current is calculated. If thisdifference does not exceed a threshold value, the process returns to thestart. If this difference does exceed a threshold value, a time delay isimplemented, as shown at block B. After this delay, which is used toreduce the likelihood of a “false alarm”, the difference is calculatedagain at block C in the same manner as block A. If the threshold is notexceeded, the process returns to the start. If the threshold is stillexceeded, block D is reached, at which it is determined whether any ofthe other pumps are currently in a cleaning mode. The drive is able tocommunicate with the other drives to determine this. It is not generallyappropriate for more than one pump to be undergoing a cleaning mode atthe same time, as this reduces the effectiveness of the sewage pumpingstation as a whole, and the cleaning mode of one pump may interrupt oradversely affect the cleaning mode of another pump. Therefore, ifanother pump is in cleaning mode, the process returns to the start. Ifno other pump in the sewage pumping station is in cleaning mode, block Eis reached at which it is determined whether the pump has alreadyimplemented its cleaning mode a maximum number of times (n) within apredetermined period of time (x). This maximum is provided to ensurethat the cleaning mode is not carried out too often, as this wouldadversely affect the ability of the pumping station to carry out itsmain function of pumping the sewage. If the maximum has been reached,the process returns to the start. If the maximum has not yet beenreached, block F is reached, at which the cleaning mode is initiated,and a cleaning cycle is carried out. The cleaning cycle involves thefrequency of the impeller of the pump being altered to de-rag the pump,as described above.

After the cleaning mode has finished, the value of n is increased byone, as shown at block G, and, after a predetermined time delay at blockH, the function returns to the start. The delay at block H ensures thattwo cleaning modes are not carried out too close together, to ensurethat the pump can be used in the meantime for its main pumping duty.

The cleaning cycle, as shown at block F, involves a predeterminedroutine in which the frequency of the pump is varied in a predeterminedmanner, which may include periods of time in which the pump operates inreverse. The predetermined routine for the cleaning mode is alsodetermined based on the measurements in the measurement phase. Thecleaning cycle comprises a plurality of phases, which depend on thepump, the topology of the pipeline and the type of pollution that ismainly in the particular wastewater well. The phases are defined bydifferent frequencies, which may be positive or negative (i.e. with thepump running in its normal direction or in revers), together with aparticular acceleration time or a deceleration time.

It will be understood that the above description of specific embodimentsis by way of example only and it is not intended to limit the scope ofthe present disclosure. Many modifications of the described embodiments,some of which are now described, are envisaged and intended to be withinthe scope of the present disclosure.

In some embodiments, the measurement phase involves the use of differentparameters. These may be more or fewer than the parameters describedabove, and may include some, all or none the parameters described above.Other parameters may be used as well or instead. Examples of otherparameters include the pump characteristic (i.e. the pump curve),including the configuration of the pipeline, the number of pumps, thenumber of other users on the pipeline, the architecture of the pipeline,pressure in the pump, the frequency of other pumps outside the sewagepumping station, but elsewhere in the sewage system.

In some embodiments, a computer carries out the tasks done by theengineer in the embodiment described above, e.g. the data correspondingto a time immediately after a manual cleaning of the pump is identifiedby the computer in detecting an indicative change in the measured activecurrent after a start of the pump.

In some embodiments, the measured parameters used by the algorithm aredifferent from those described above. These may be more or fewer thanthe parameters described above, and may include some, all or none theparameters described above. Other parameters may be used as well orinstead.

In some embodiments, the determination phase is carried out differently,for example with some or all of the blocks described above omitted. Theskilled person will appreciate that various implementations may becarried out in the determination phase without departing from the scopeof the present disclosure.

In some embodiments, the expected electric current calculated by thealgorithm is not the active current, as described above, but is insteadthe total current output from the drive.

In some embodiments, the cleaning cycle is not created specifically forthe drive, but a standard cleaning cycle is used by the drive.

In some embodiments, some or all of the functionality described abovewhile the drive is in use is implemented on a device separate from thedrive. The drive may be, for example, simply informed when to implementits cleaning mode after the other steps have been carried out on theother device.

In some embodiments, the drive is in communication with one or moredrives in at least one other sewage pumping station within the sewagesystem. This enables the drive to be aware of the situation at the atleast one other sewage pumping station, which may be upstream ordownstream from the sewage pumping station to which the drive isassociated.

In some embodiments, the pumps in the sewage pumping station areconfigured to operate in a variable flow rate system (in normal use),rather than a constant flow rate system, as described above. In someembodiments, the pumps in the sewage pumping station are configured tooperate in either system.

In some embodiments, the pump(s) in the sewage pumping station aresituated outside the wastewater well.

1. A method for configuring a drive to control the operation of a pumpin a sewage system, the method comprising: measuring at least oneparameter of the sewage system; using the measurement of the at leastone parameter to create an algorithm for the drive to control theoperation of the pump; and configuring the drive to use the algorithm tocontrol the operation of the pump.
 2. A method as claimed in claim 1,wherein the drive is configured to use the algorithm to determine whento implement a cleaning mode of operation for the pump.
 3. A method asclaimed in claim 1, wherein the algorithm is configured to calculate anexpected electric current for the drive for a given operating conditionof the drive.
 4. A method as claimed in claim 3, wherein the expectedelectric current is the active current drawn by the pump.
 5. A method asclaimed in claim 3, wherein the drive is configured to monitor an actualelectric current in use corresponding to the expected electric currentand optionally wherein the drive is configured to compare the actualelectric current with the expected electric current for the presentoperating condition of the drive.
 6. A method as claimed in claim 5,wherein, based on the comparison of the actual electric current with theexpected electric current, the drive is configured to determine whetherto alter the operation of the pump.
 7. A method as claimed in claim 1,wherein the at least one parameter comprises an output frequency of analternating current output by the drive.
 8. A method as claimed in claim1, wherein the at least one parameter comprises a wet well level of awet well in the sewage system, the wet well being associated with thepump controlled by the drive.
 9. A method as claimed in claim 1, whereinthe at least one parameter comprises a number of pumps active in asewage pumping station in the sewage system, the sewage pumping stationcomprising a plurality of pumps including the pump controlled by thedrive.
 10. A method as claimed in claim 1, wherein the at least oneparameter comprises an output frequency of an alternating current outputby another drive in a sewage pumping station in the sewage system, thesewage pumping station comprising a plurality of pumps including thepump controlled by the drive.
 11. A method as claimed in claim 1,wherein the drive is one of a plurality of drives configured to operatein the sewage system, each of the drives being configured to drive arespective pump of a plurality of pumps in the sewage system.
 12. Amethod as claimed in claim 1, wherein the sewage system comprises asewage pumping station, in which the pump is situated and optionallywherein the sewage pumping station comprises a plurality of pumps, eachof the plurality of pumps being operable by a respective drive, andfurther optionally wherein the drive is configured to communicate withat least one other drive associated with a respective other pump in thesame and/or another sewage pumping station.
 13. A method for creating analgorithm for a drive to operate a pump in a sewage system, the methodcomprising: measuring at least one parameter of the sewage system; andusing the measurement of the at least one parameter to create analgorithm for the drive to control the operation of the pump.
 14. Acomputer-readable medium comprising an algorithm created by the methodof claim
 13. 15. A drive configured to control the operation of a pumpin a sewage system using an algorithm created by a method comprising:measuring at least one parameter of the sewage system; and using themeasurement of the at least one parameter to create the algorithm.
 16. Adrive configured by the method of claim
 1. 17. A drive configured by themethod of claim
 13. 18. A sewage pumping station comprising at least twopumps controlled by respective drives each according to claim 15,wherein the algorithm created for each respective drive is different andoptionally wherein the algorithm created for each respective drive isbased on a respective operating condition for the respective drive. 19.A sewage pumping station comprising at least two pumps controlled byrespective drives each according to claim 16, wherein the algorithmcreated for each respective drive is different and optionally whereinthe algorithm created for each respective drive is based on a respectiveoperating condition for the respective drive.
 20. A sewage pumpingstation comprising at least two pumps controlled by respective driveseach according to claim 17, wherein the algorithm created for eachrespective drive is different and optionally wherein the algorithmcreated for each respective drive is based on a respective operatingcondition for the respective drive.